It has been a common practice in the refuse collection industry for a single refuse receiving vehicle to service both residential and commercial establishments. Traditionally, residential refuse receptacles were approximately thirty gallon containers, which the vehicle operator lifted by hand to dump into the refuse receiving cavity of the vehicle. In contrast, commercial refuse containers are typically much larger steel containers, often two cubic yards or greater, and commonly referred to as "dumpsters." These containers are typically pivot-dumped into the refuse receiving cavity by mechanically tipping the container over the rear edge of the refuse receiving cavity. Such containers are usually tipped by a cable and winch or by a hydraulically actuated tipper bar that rotates and lifts the container.
More recently, it has become popular in some residential areas to use larger, plastic roll-out refuse receptacles that have a capacity of approximately ninety gallons. Typically these refuse receptacles have two lifting handles along a common exterior receptacle wall, and two wheels for convenience in moving the receptacle. As a result of the greatly increased size over prior residential receptacles, the roll-out residential receptacles are not easily lifted by hand. This has given rise to the development and use of refuse receptacle lifters specifically made for the newer larger roll-out receptacles.
An example of a commercially successful refuse receptacle lifter for use with the larger roll-out residential receptacles can be seen, for example, in U.S. Pat. No. 5,069,593. The lifter, as generally shown in the patent, has been marketed as the "Tuckaway" dumper by Perkins Mfg. Co. of Chicago, Ill. This lifter may be retracted to a lower position, where it does not interfere with the dumping of commercial containers by cable and winch. However, the particular Tuckaway lifter shown in the patent cannot be used on a vehicle equipped with a tipper bar for dumping commercial containers, because the lifter would obstruct the path of movement of the tipper bar.
A receptacle lifter has been designed to work in concert with the movement of a tipper bar. Such a lifter is disclosed in abandoned U.S. patent application Ser. No. 378,823, filed May 12, 1982 and entitled Lifting Mechanism for a Sanitation Vehicle. The lifter shown in that application has been used commercially and includes a plate which pivots at its upper end at the rear edge of the refuse receiving cavity and is pushed upward by activation of the tipper bar itself. However, while this lifter does not prevent the movement of the tipper bar, actuation of the lifter to dump residential receptacles requires full activation of the tipper bar mechanism, which consequently causes a significant increase in the number of times the tipper bar must be cycled. This, in turn, may result in higher maintenance costs and decreased life expectancy for the tipper bar hardware. Also, the tipper bar cycle time is often greater than the desired cycle time for a receptacle lifter, therefore increasing the time required for refuse collection.
At least one manufacturer, Bayne Machine Works, Inc., of Simpsonville, S.C., markets a receptacle lifter that has its own hydraulic drive and is capable of use with a vehicle equipped with a tipper bar. The Bayne lifter exhibits certain features common among the prior art; specifically, the means for engaging the lifting handles of the roll-out residential receptacles includes an upper hook for lifting an upper lifting handle on the receptacle and a lower hook which engages over a lower handle on the receptacle to keep the receptacle from falling into the vehicle cavity when the receptacle is inverted for dumping.
With the Bayne lifter, the lower hook retracts to a raised position when the lifter is lowered in order to allow passage of the tipper bar beneath the lifter. As a roll-out residential receptacle is being lifted and inverted, the lower hook moves downwardly to engage the lower receptacle handle. However, a shortcoming of the Bayne dumper is that the lower hook continues to move even after having engaged the lifting handle of the receptacle. This continued movement may impart undue stress on the handles, resulting in bending the handles or breaking the receptacle.
Another example of a receptacle lifter for use with a vehicle equipped with a tipper bar can be seen in U.S. Pat. No. 4,673,327 to Knapp entitled "Waste Receptacle Dumping Apparatus." The Knapp patent discloses a device that has upper and lower hooks that move apart during the initial portion of the lifting cycle to engage the lifting handles of a rollout receptacle and then do not move appreciably further apart over the remaining pivotal movement. However, the lifter shown in Knapp is directly pivotally attached to the mounting support at the cavity opening. Direct pivotal attachment limits the height and forward displacement attainable by the dumping apparatus for reaching forward into the cavity to dump receptacles. The inherent reach limitations of the Knapp device result in the refuse being dumped close to the rearward edge of the cavity. This, in turn, may create a need for more frequent cycling of the vehicle's refuse compacting equipment in order to keep the refuse from falling out of the vehicle. More frequent cycling of the compacting equipment, of course, requires additional operator time.
Another drawback common with prior art receptacle lifters is that the lower engagement hook projects a fixed distance from the face of the lifter, and is unable to adapt to potential variations in receptacle dimensions, e.g., variations in the space between the receptacle wall and the lower handle or in the particular shape of the receptacle wall adjacent the handle. Because the lower handle of the receptacle is not always the same distance from the container wall, the projecting lower hook of prior art receptacle lifters may actually puncture the side wall of a receptacle, or downward movement of the hook may scrape or tear the side wall.